Monday, July 18, 2005

Redtail Molts: Questions & Answers

Ben Cacace, a long-time Central Park Hawk observer, sent me a question which I forwarded to John Blakeman. He answered, I asked for another clarification and he answered again. Below is the entire correspondence:

Marie,

I have a question for you concerning molting ofRed-tailed Hawks. Could you or Blakeman let me knowwhat the sequence of molting is for Red-tailed Hawks?I have a few books at home but they don't go into thedetails on the timing of the molt. I am wondering whenthe juvenile starts molting the tail feathers. This isrelated to the molting RT I saw perched on the SouthGate House of the reservoir recently. Only one half ofone adult tail feather had grown in. This was on July15th 2005. Here is the quote I posted to eBirds NYC:

"At the reservoir on the top of the South Gate Housewas a subadult Red-tailed Hawk. This RT is the firstI've seen that is molting from juvenile to adult. Themajority of the juvenile tail feathers were intact andunderneath the worn feathers, in the center of thetail, is a half-length bright brick-red tail feather.The iris of this hawk is light in color. It had a darkbelly-band and a dark head."

Even though it was very hot and it was on an asphaltroof it spread itself out flat, wings stretched andtail spread, apparently looking to absorb as much heatas possible. This was done for a number of minutes.

Thanks in advance!

Ben

John Blakeman replied

Ben,

What you've seen, with the immature red-tail flying around with a single, half-descended red tail feather, is rather normal.

By this late in the season, the bird should have 4 to 6 red tail feathers in place. But the onset and progression of annual molting, both for immatures and old adults, can vary widely, for reasons not always clear. It seems that well-fed birds often start earlier and finish the molt early. Birds having difficulty finding food often start later and progress slowly. That's probably the case with the bird you are watching.

But don't be surprised to find several gaps in the tail where feathers have been dropped in a few weeks. In August, time gets short and molting sequences are usually advanced. I once had an immature red-tail that had a delayed molt (even though she had plenty of food from me -- I'm a falconer). Then, in late July and August she just seemed to drop feather after feather. In August she looked plainly ragged. But by October, she had a new, adult set of feathers.

The tail molt usually begins with a central feather, and then progresses outwardly as new feathers descend and harden.

Hope this helps understand what you've seen.

Keep me posted. Shoot any other RT questions my way.

Sincerely,

John A. Blakeman

I wrote Blakeman back:

John, I want to be sure I get it right. The immature bird discussed below is not a 2005 fledgling, right? This year's crop won't have any red in their tails until 2006??

Marie,

Right. I didn't make that clear. Any bird molting right now was alive and on the wing last year. This molting red-tail fledged in the spring of 2004. Every bird of every age has to take its feathers through a fall, winter, and spring before they molt out.

I also didn't point out that the new tail feathers will be about an inch shorter than the original brown feathers the bird left the nest with. By now, when molting birds are about one-third to half way through their molts, the tails can look a bit imperfect, with the older ragged feathers extending a bit beyond the bright new red feathers.

The same thing happens with the long primaries, the finger-like feathers on the tips of the wings. This is why first year red-tails, in their immature brown plumage, not only look larger than adults, they physically are -- in dimension, not weight. Because flight and leg muscles haven't completely matured when the birds fledge, the birds are able to fly with moderate ease with the longer feathers. This gives first year birds lighter wing loading. But with stronger muscles in the second year, the tail and wings molt out shorter. Hawk watchers should understand that first year red-tails look, and are, larger than the adults. They aren't as fast or strong, just bigger. They don't weigh as much, either.

But this is always a confusion for the unfamiliar. The presumption is that a small hawk is a "baby," and a big one an adult. Doesn't work that way. It's not size. It's weight that counts. What can the bird hunt and kill? That depends on muscles, and they develop more slowly than feathers.

So no one should ever be surprised to see a pair of eyasses about to fledge that appear larger than their parents. In size, they will be. That gets fixed in next year's molt.